Patent document 1 discloses a navigation apparatus, in which when a user deviates from a guidance route and then returns to the guidance route, a shift route from a deviation point to a return point is recorded as a difference route. The navigation apparatus adopts the difference route preferentially as a route from the deviation point to the return point at the subsequent retrievals of guidance routes. The subsequent calculation for a guidance route thus reflects the road which the user decided to pass even though deviating from the guidance route. This allows a route guidance or navigation to meet the user's preference.
In addition, Patent document 2 discloses a technology, which records points a user accesses, and proposes, as a destination candidate, a point extracted from the recorded points.
In the technology in Patent document 1, a guidance route is calculated and acquired only when a user sets a destination point uniquely; namely, if a guidance route is not present, the technology does not function at all.                Patent document 1: JP-2001-124578 A (corresponding to U.S. Pat. No. 6,418,373)        Patent document 2: JP-2007-10570 A (corresponding to USP-2007/0005242)        